Tapered piston pin

Abstract

A tubular piston pin for an internal combustion engine being of lightweight and high strength design with a cylindrical exterior surface and a double hourglass shaped aperture defined by thin-walled end portions; a thin-walled intermediate portion and two thicker-walled portions therebetween. A method for easy and inexpensive piston pin manufacture includes: the formation of half pins by molding a metal slug between two dies each having tapered end portions, punching out a midportion or intermediate web or wall to form an aperture therethrough with a generally hourglass shape, and aligning and joining two half pins axially together to form a piston pin with the double hourglass shaped interior aperture.

I claim: 
     
       1. A method of manufacturing a tubular piston pin having a cylindrical exterior surface and a contoured interior surface in the form of a double hourglass shaped aperture extending axially therethrough and characterized by opposite thin-walled end portions and midportion and by thicker-walled portions therebetween, comprising these steps: supporting a metal cylinder in a cylindrical bore of a rigid housing, both having equal diameters;   molding the metal cylinder by moving a pair of dies in opposite directions each against an opposite end face of the metal cylinder to produce a substantially tubular half pin with thin-walled end portions and a thicker-walled midportion including a radially extending wall thereacross;   striking out the radially extending wall of the half pin to produce a continuous aperture axially through the half pin and having a substantially hourglass shape;   axially aligning two half pins and integrally joining the abutting ends thereof to produce a piston pin of twice the length of the half pin having a double hourglass configured aperture extending axially therethrough.   
     
     
       2. The method of manufacturing the piston pin set forth in claim 1 in which the pin halves are joined by welding. 
     
     
       3. The method of manufacturing the piston pin set forth in claim 2 in which the weld is created by electron beam energy. 
     
     
       4. The method of manufacturing the piston pin set forth in claim 2 in which the weld is created by friction energy. 
     
     
       5. The method of manufacturing the piston pin set forth in claim 2 in which the weld is created by laser energy. 
     
     
       6. The method of manufacturing the piston pin set forth in claim 1 in which the end portions of the dies adapted for molding the metal cylinder have a generally tapered configuration with a relatively large diameter base and a progressively smaller outward dimension. 
     
     
       7. The method of manufacturing the piston pin set forth in claim 1 including a final step of grinding the external cylindrical surface of the piston pin to remove any weld residue.